Miniature trip-free circuit breaker



Aug. 9, 1966 M. B. WOOD MINIATURE TRIP-FREE cmcun' BREAKER 2 Sheets-$heet 1 Filed Oct. 19. 1964 9 m u 1 F m w 5 1!. 5 .1 0 4 w w .n i J W 6 w I 3 E a a 7. -0 Mr I: 6 w M x 0. W 0 Z 24 6 a 6 2 w 3 3E mu w a 4 ww 6 0 w .F/v L El|h n g: wn u 3 a l u L 4 V: n m w E 6 5 6 5 E 3 .55 72215 Attorney W M Aug. 9, 1966 M, B. WOOD MINIATURE TRIP-FREE CIRCUIT BREAKER 2 Sheets-Sheet 2 Filed Oct. 19. 1964 United States Patent 3,265,835 MINEATURE "KEEP-FREE CIRCUIT BREAKER Morris B. Wood, Ameshury, Mass. (R0. Box 546, Ipswich, Mass. @9138) Filed Oct. 19, 1964, Ser. No. 4494,7913 9 Claims. (Cl. 200 116) The present invention relates to electrical overload, trip free circuit breakers and more particularly to improvements in a circuit breaker disclosed in United States Letters Patent No. 2,613,296, granted October 7, 1962, upon application of the present inventor.

Probably the greatest problem in constructing a highly compact high capacity circuit breaker is surface leakage along inner walls of anenclosing frame. The next problem Which may be difficult to solve is in obtaining contact opening distance, required to prevent continuous arcing of the contacts under a heavy overload, such as may be met with 110-220 volt service. This requirement may be solved by quick opening of the contacts and the use of an effective magnetic blow-out action on the arc.

To meet these requirements the present circuit breaker has been constructed with asize of about one-halfthe linear dimensions of any present day available circuit breaker and without sacrificing the necessary features.

In the breaker of the patent referred to, the circuit is "opened by-separ-ating a single movable contact from a fixed contact and the movable contact is connected to a bimetallic latch for securing the contacts closed by a flexible conductor which is subject to displacement, fraying and bending with each opening and closing movement of the contacts. In other respects the inherent arrange ment ofparts in the prior breaker is such that there is considerable unused space within an insulating frame containing it,-unless the dimensions are reduced and the current interrupting ability is severely limited by a relatively short gap provided between the contacts when they are opened with consequent arcing and pitting of the contacts and shortness of possible surface leakage paths between the fixed contact and the closest point of engagement in the frame-with the flexible conductor.

With these difficulties in view, the objects of the present invention are to enable effective manufacture by quantity production methods of a more compact form of circuit breaker having greater current interrupting capacity, less arcing and pitting of the contacts and greater durability with more uniformity and reliability in results.

In the attainment of these objects, a feature of the invention resides in a circuit breaker having two pairs of contacts, one movable and one fixed in each pair being connected in series. All other things being equal, twice the total contact opening gap is formed and in breaking the circuit an accentuated magnetic arc blow out action is caused to take place. The blow out action is produced by mounting the contacts on a common U-shaped carrier and the bimetallic latch comprises a U-shaped strip arranged in spaced parallel relation to the contact carrier in a manner to concentrate magnetic flux about the contacts. Also, because the flux produced by the carrier and the latch is opposed, similar forces react on the carrier and strip to aid in tripping the breaker when heavy overloads occur.

In one form of this feature, the bimetallic strip is engaged by an adjusting screw arranged with its head projecting outside the frame to facilitate initial calibration I of the breaker.

These and other features of the invention, as hereinafter described and claimed will readily be apparent to those skilled in the art from the following detailed specification, taken in connection with the accompanying drawings, in which:

overload current.

FIG. 1 is a view in side elevation, partly in section and on a two for one scale with one side of an enclosing frame removed to show the operating mechanism of a circuit breaker embodying the features of the present invention;

FIG. 2 is a view in left end elevation of the circuit breaker illustrated in FIG. 1;

FIG. 3 is a sectional view in left end elevation and in section taken along the line III-III of FIG. 1;

FIG. 4 is a sectional plan view of the circuit breaker of FIG. 1, taken along the line IV-IV of that figure; and

FIG. 5 is a partial perspective view on a further enlarged scale of the electrically conductive parts of the breaker together with the operating plunger for manually opening and closing the contacts.

The illustrated electrical overload circuit breaker is of the bimetallic strip trip-free type wherein a single manual operating button is utilized to open or reset the breaker into current conducting condition but is incapable of holding the contacts from separation under conditions of This is accomplished, as in the breaker of the prior patent, which is provided with apair of actuating members, one forming a carrierfor themovable contacts by which they are engaged with the fixed contacts and the other comprising a detent by which the contacts are held latched against separation except when an overload current flow exists, the contacts being opened by' springs which also act to shift the button to a circuitopen position. In this way an indication is given by the position of the button when the circuit breaker is tripped by overload current. a

The operating button for thebreakeris indicated at 10, and the actuating members comprising a carrier and a detent at 12 and 14. The bimetallic strip which is U- shaped, acting upon the occurrence of a flow of overload current is shown at 16, the circuit opening springs at 18 (see FIG. 4) and the movable contacts at 20 and 22', a latch in the form of a bar 13 being secured to the i base of the U formed by the strip. The contacts of the breaker are arranged in two pairs to provide a series, double break distance thus affording twice the circuit opening gap as where asingle pair of contacts is used. One movable contact faces toward a fixed contact 24 or 26 in each pair and the fixed contacts both face in the same direction to simplify mechanical construction. For

this purpose one of the fixed contacts is secured to a terminal post 28 comprising one of a .pair and the other of the fixed contacts is secured to a plate 34). The .movable contacts are both mounted at spaced ends of the common carrier .12, which is also U-shaped and shiftable toward and from the fixed contacts to open and close a circuit through the breaker. The other in the pair of terminal posts is shown at 32 and has secured to it one end of the bimetallic strip 16. The other end of the strip is secured to the plate 30.

In order to avoid the use of a flexible conductor connected to either of the movable contacts, thereby preventing the possibility of reducing the effective length of surface leakage paths along the frame and also to alleviate pitting by blowing out magnetically any arcs which form between the contacts, besides providing a quick magnetic assist in tripping. the breaker upon the occurrence of severe overloads, according to the present invention, the U-shaped portions of the contact carrier and the bimetallic strip are connected in series and are arranged inspaced parallel relation with the current flowing through them in opposite directions, as illustrated by the arrows in FIG. 5. For this reason the magnetic fiux path created by the current flow through the bimetallic strip opposes that through the U-shaped portion of the contact carrier, the ends of both being pointed in the same direction. The opposing flux of the strip and carrier tends to become most concentrated and to produce the greatest turbulence in its lines of force about the open ends of the strip and carrier, so that a very effective magnetic blow-out results for any arc occurring between the contacts. Also, with a sudden heavy overload there is a repulsion force exerted in the flux between the strip and the carrier acting to assist the flexing force produced by heating the bimetallic strip to cause a much accelerated opening of the contacts.

When the latch plate 19 holds the detent, as in FIG. 1, and the button is depressed two rolls 38 rotatable on a pin 40 secured between two projections from the contact carrier 12 are forced along an angular portion of the detent to press the movable contacts into engagement with the fixed contacts. To insure that the movable contacts are maintained in alinement with the fixed contacts the two parts 34 and 36 of the frame have guiding slots 41 (FIG. 4) entering their inner surfaces and steel studs 42 and 44 project from the carrier into the slots. The

rolls 38 enter partway into a slot 46 (FIG. 3) at the lower end of the button 10 and between the rolls is a link 48 pivoted to the roll supporting pin 40 at its lower end and connected at its upper end by a pivot 50 passing through a mid portion of the button, the link swinging in a narrower portion of the slot 46. When the latch plate on the bimetallic strip 16 releases the detent the springs 18 pull the carrier and the movable contacts away from the fixed contacts to open the circuit.

The force of the two springs 18 is sufiicient to open the contacts quickly and is adequate to press the detent to the right, as viewed in FIG. 1. As shown in this figure, the detent is suspended for swinging movement on a rod 52, the ends of which are confined in recesses in the inner surface of the two frame parts 34 and 36. Also surrounding the rod 52 are the coils of a rat trap spring 54 acting at its ends on the frame and at its central portion on the detent to maintain it in contact with the rolls 38, the force of the spring 54 being much weaker than that of the circuit opening springs 18. To secure the springs 18 in place they are hooked about a stud 55 having its ends inserted in recesses of the frame parts, the other ends being hooked about the studs 42 and 44. Thus, after being pressed to the right the angular portion of the detent swings beneath the rolls and tends to force them upwardly until the button 10 is raised to its dotted position of FIG. 1. Similarly, if the detent is not released by action of the bimetallic strip but the botton is pulled upwardly the circuit is also opened by the contacts independently of the detent.

As soon as the button moves upwardly after tripping the breaker the rolls 38 move above the projecting portion of the detent 14 and the detent is permitted to swing back to latched position. The breaker is now in condition to be reclosed merely by depressing the button 10 without further resetting effort.

The terminal posts 28 and 32 are secured in slots cut into edge faces of the frame part 34 and the posts are shaped to bring their lower ends into offset relation as shown in FIG. 2. To secure the terminal posts more effectively in position, the post 28, on which the contact 22 is fixed, is bent sharply through 180 to surround a protrusion 56 from the frame part 36. The terminal post 32 is secured in place as it runs along the bottom wall of the frame part 36 by entering a shallow groove 58 (see FIG. 3) in the side of that frame part.

For adjusting the tripping action of the bimetallic strip 16, the end which is secured to the contact plate 30, is engaged along its underside by the upper end of a screw 60 threaded into the contact plate and arranged with its lower slotted end to be exposed for turning with a screw driver through a recess in the frame part 36. By means of the screw 60 any variations in the parts resulting from assembly or changes needed in the requirements to be met may be compensated for.

To prevent displacement of the button toward or away from the fixed contacts in the frame each frame part has an internal slot 62 (FIG. 1) opposed to one in the other, frame part, running parallel to the length of the button. The button in turn has guiding projections 64 entering the slots. These projections not only keep the button in line with the other parts but prevent it from turning in a ferrule 66 secured to a clamp plate 68, in which the plunger slides.

To increase the surface leakage path between the fixed contacts the adjacent edges of the frame parts are partly cut away to receive an insulating plate 70, passing between the ends of both the bimetallic strip 18 and the contact bearing ends of the contact carrier 12. In this way the contact carrier surrounds the insulating plate to increase the surface distance between the ends of the carrier supporting the movable contacts.

To hold the parts of the frame 34, 36 together after the breaker has been assembled the clamp plate 68 has four tabs fitting within recesses at the upper corners of the frame. The tabs are perforated and have passing through them two pins 72 headed over at their ends to prevent separation. The bottom wall of the frame is also formed with thickened walls through which a third pin 74 (FIG. 1) passes to hold the frame parts in position with the insulating plate secured between them.

The nature and scope of the invention having been set forth and a particular embodiment having been described, what is claimed is:

1. A circuit breaker having two pairs of contacts, one movable and one fixed in each pair, the fixed pair both facing in the same direction, a pair of terminal posts, to one of which one of the fixed contacts is secured, a plate to which the other of the fixed contacts is secured, a U- shaped common carrier for the movable contacts, shiftable toward and from the fixed contacts to open or close a circuit through the breaker, in combination with a U-shaped bimetallic strip arranged in spaced parallel relation to the contact carrier with one end secured to the contact plate and the other end to the other in the pair of terminal posts and provided with a latch bar between its ends acting to hold the carrier against retraction from the fixed contacts but movable with the strip away from contact carrier holding position to enable the movable contacts to be disengaged from the fixed contacts.

2. A circuit breaker, as in claim 1, in which the ends of the bimetallic strip are pointed in the same direction as those of the contact carrier to concentrate magnetic flux created by current flow through the said strip and carrier into the area of the contacts.

3. A circuit breaker, as in claim 2, in which the current in the strip and carrier flows in opposite directions to apply a repulsion force between them.

4. A circuit breaker, as in :claim 1, in which there is provided a bimetallic strip adjusting screw, threaded into the contact plate and arranged to bear against one arm of the U-shaped strip and to be exposed for adjustment through the frame at the other end.

5. A' circuit breaker, as in claim 1, in which there are provided a two part hollow insulating frame having a division plane passing between "both contacts of each pair and forming an enclosed space about the contacts and an insulating plate secured between opposite sides of the frame parts and passing between the ends of both strip and contact bearing ends of the carrier.

6. A circuit breaker, as in claim 5, in which the contact carrier is U-shaped and surrounds the insulating plate to separate the contacts.

7. A circuit breaker, as in claim 1, in which there are provided actuating mechanism, including a U-shaped carrier, a roll rotatable between projections from the base of a manual operating button for moving the roll and the carrier, a swinging detent along which the roll moves to cause the carrier to close the contacts, a two part hollow insulating frame forming an enclosed space about the contacts and having internal opposed slots running parallel to the length of the button and guiding projections from the button entering the slots to prevent displacement of the button toward or away from the fixed contacts.

8. A circuit breaker, as in claim 7, in which the button is slotted and there is provided a link pivoted at one end within the slot of the button and pivoted at the other end tothe carrier, the roll being rotatable about the pivot pin between the link and the contact carrier, a swinging detent arranged to engage the latch bar on the bimetallic strip at one side of the roll to enable the plunger to open-the contacts independently of the detent.

9. A circuit breaker, as in claim 8 in which a pair of springs are stretched between the contact bearing end of the carrier and the frame, one at either side of the plunger.

References Iited by the Examiner UNITED STATES PATENTS 5/1940 Frank 200-88 X 6/ 1940 Frank. 12/1951 Marcoz a 200-116 11/ 1952 Boller et al 200-88 12/ 1953 Casey 20088 X 11/1960 Brackett 200-116 FOREIGN PATENTS 7/ 1947 France.

BERNARD A. GILHEANY, Primary Examiner. 

1. A CIRCUIT BREAKER HAVING TWO PAIRS OF CONTACTS, ONE MOVABLE AND ONE FIXED IN EACH PAIR, THE FIXED PAIR BOTH FACING IN THE SAME DIRECTION, A PAIR OF TERMINAL POSTS, TO ONE OF WHICH ONE OF THE FIXED CONTACTS IS SECURED, A PLATE TO WHICH THE OTHER OF THE FIXED CONTACTS IS SECURED, A USHAPED COMMON CARRIER FOR THE MOVABLE CONTACTS, SHIFTABLE TOWARD AND FROM THE FIXED CONTACTS TO OPEN OR CLOSE A CIRCUIT THROUGH THE BREAKER, IN COMBINATION WITH A U-SHAPED BIMETALLIC STRIP ARRANGED IN SPACED PARALLEL RELATION TO THE CONTACT CARRIER WITH ONE END SECURED TO THE CONTACT PLATE AND THE OTHER END TO THE OTHER IN THE PAIR OF TERMINAL POSTS AND PROVIDED WITH A LATCH BAR BETWEEN ITS ENDS ACTING TO HOLD THE CARRIER AGAINST RETRACTION FROM THE FIXED CONTACTS 